1. Field of the Invention
The invention relates to a light emitting device, and more particularly, to a light emitting device using a light emitting diode as light source.
2. Description of Related Art
As the technology for light emitting diode (LED) grows, light emitting diodes have gradually taken the place of traditional bulbs in lighting field. Since the conventional light emitting diodes are driven by direct current (DC), the conventional light emitting diodes can only be applied in DC-driven environments. Or, AC-DC converters and voltage transformers are needed for transferring the conventional alternating current (AC) to the lower voltage direct current so as to provide DC to light emitting diodes.
However, the commercially available electricity is usually 110V/220V alternating current. Therefore, there exists an inconvenient trouble of the conventional light emitting diodes by using direct current. Accordingly, some researchers developed alternating current light emitting diode (AC LED) or high voltage light emitting diode (HV LED). For AC LEDs, extra voltage transformers, rectifiers, or driving circuits are not required, and AC LEDs can be driven by applying alternating current directly. For HV LEDs, the transformation for lower voltage direct current is not required, and HV LEDs can be driven by conventional direct current, hereby reducing energy consumption occurred in voltage transformers.
Currently, the AC LED/HV LED both are made for forming light emitting unit matrix and internal connection circuits on a miniature-sized single chip, using the internal connection circuits to connect a plurality of light emitting diode in series or in parallel, such that the AC LED/HV LED may have the ability to adjust voltage and current. Generally, the internal connection circuits usually adopt transparent conductive materials, such as indium tin oxide (ITO). Since the internal connection circuit can only provide the effect of electrical connection, the light emitting efficiency is lower at the bridging portion of two adjacent light emitting diodes.